JPS61182879A - Method in electric-arc machining machine and sensor constitution - Google Patents

Abstract

In a processing machine which operates with an arc, for example, a burning cutting installation, the arc current is measured and regulating signals are derived from the measurement value for the purposes of regulating the tool-workpiece spacing. In that procedure the analog measurement value is converted by a converter into high frequency signals whose frequency corresponds to the respective measurement value, the high frequency signals are fed to a regulator and therein are converted again into analog and/or digital signals. Also provided is a capacitive or inductive spacing measuring means which is also connected to the converter so that the arc current measurement values and the spacing values of the capacitive or inductive measuring arrangement are processed by the same converter means and evaluation circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for determining the distance between a tool and a workpiece in an electric arc processing machine, and more particularly, the present invention relates to a method for determining the distance between a tool and a workpiece in an electric arc processing machine, and in particular, by measuring the voltage and/or current of an arc, and determining the measured voltage and/or current value. The present invention relates to a method for determining the distance in an electric processing machine, which is equipped with a first measuring means for generating an electrical analog signal corresponding to the arc length VC.

BACKGROUND OF THE INVENTION In processing machines using electric arcs, control and adjustment of arc length is an important consideration in obtaining desired results. For example, the quality of the weld seam obtained by an electric welder is highly dependent on the arc length between the electrode and the workpiece. The same applies to the removal, addition, and combination of materials in fusing equipment and other arc processing machines and processes.

As is known, arcing occurs in this type of machine due to the flow of electrical current, preferably high level direct current, between the tool and the workpiece. Once the arc is ignited, even at a fairly low DC voltage, there is a considerable tolerance.
It is possible to confine the arc length and processing range to plasma. In the case of similar tools (for example, welding electrodes) and workpieces (base metals), the burning voltage and current correspond to the arc length. This idea has been put to practical use in follow-up adjustment devices (feedback control devices) for fusing equipment. That is, measure the burning current or voltage between the tool and the workpiece, compare it with the reference value, and detect the deviation.
The distance t between the tool and the workpiece is adjusted until the reference value and the measured value match again.

In this way, the spacing between the tool and the workpiece can be controlled very precisely, making it extremely useful for continuously adjusting the spacing, even when working with workpieces with irregular surfaces, such as corrugations. It is. An example of this type of device is Masser.
Grinshetrn (Frankfurt) Yotsu, LI
It is commercially available under the name BO-Rtrgg lung.

This method is called a processor-oriented sensor type.

In the prior art, there are difficulties in adjusting the tool/workpiece spacing when the tool is initially brought close to the workpiece, ie, before the arc is ignited.

A similar problem occurs when the arc is extinguished due to a failure or the like during processing. This movement of approaching the workpiece is generally done by first finding the sp.
acinrt).

To solve the problem of adjusting the spacing between the tool and the workpiece during the automatic advance mode, the prior art uses a separate, dedicated adjustment device in addition to the adjustment device for the arc. This adjustment device generally uses an inductive or capacitive sensor, which is activated during a spacing advance mode to continuously measure the spacing between the workpiece and the tool, ultimately obtaining a reference spacing. After ignition of the arc, the regulating device is de-energized and removed from the operating range of the tool by mechanical means.

Therefore, this method requires an entire sensor arrangement just for advance estimation of the spacing between the tool and the workpiece;
Since the sensor device is not used during machining operation, the cost of the entire device is considerably high. Furthermore, when generating the regulated voltage from the arc voltage and current, it is necessary to insulate and separate the two, which is very expensive. Furthermore, it is detected and regulated as a DC voltage,
The measurement signal corresponding to the arc length, which is transmitted to the evaluation device, may be influenced by electromagnetic interference on the transmission path, resulting in inaccurate adjustments.

The object of the present invention is to eliminate the drawbacks of the prior art described above, and in particular, by improving the apparatus and method described at the beginning of this specification and combining sensors in a very effective manner. The purpose of the present invention is to provide an economically advantageous and reliable device and method.

According to the present invention, the above object is to first convert an analog signal corresponding to the arc length into a high frequency signal in a measuring means for measuring arc voltage or current, and send this high frequency signal to a regulator through a transmission circuit, particularly an electric line. , where it is converted into an analog and/or digital signal again by passing it through a converter, and the output signal of the converter is given to a display and/or an adjustment device that adjusts the distance and arc length between the tool and the workpiece. , basically solved.

Surprisingly, the above configuration provides two major benefits without increasing component costs. That is, by converting an arc length-dependent DC signal into a frequency signal, an ordinary LC sensor device can be used not only for advance tool/workpiece spacing, e.g. by capacitive or inductive measuring devices, but also for arc operation. It can also be used for adjustment. Furthermore, since the measurement signal is transmitted between the sensor and the regulator using a high frequency signal, the sensitivity to electromagnetic interference is considerably lower than when transmitting an analog signal. Therefore, the configuration according to the present invention is versatile, simple in construction, accurate, and resistant to electromagnetic interference.

In a sensor configuration with a second measuring means for measuring the tool/workpiece distance via a capacitive or inductive sensor when the arc is off or not fully operational, a high-frequency signal is analog and/or
Alternatively, the invention can be further improved by supplying a high frequency signal to a sensor which is also connected to a first converter that converts it into a digital signal. Both the measured value signal for the arc and the distance proportional signal obtained from the capacitive or inductive sensor can be processed by the same circuit arrangement. More specifically, while conventional measurement means with sensor configurations include only one capacitive or inductive sensor as a frequency varying element of an LC circuit, generally an oscillating circuit, the present invention uses this type of sensor. A second frequency varying element is provided in the circuit such that its frequency characteristic varies not only with the sensor/workpiece spacing, but also with the spacing proportional signal obtained from the arc voltage/current by the first measuring means.

Examples of conventional sensors and LC circuits of the type described above are described in the following German published applications by the same applicant: US Pat.

DB-O8 No. 2726648 (filed on June 14, 1977), DH-O8 No. 2829851 (July 7, 1978)
DE-O8 No. 2747539 (No. 1 of 1977)
(filed on 22nd October) and Swiss Patent Application No. 641989 (
(filed on December 20, 1979).

Therefore, it is up to those skilled in the art to appropriately select which of the inductance and capacitance of the LC circuit to use as the nt-frequency varying element, ie, the sensor, according to the specific usage situation. Incidentally, a circuit configuration in which the LC circuit is part of the oscillator circuit has been found to work well. However, the LC circuit may be part of a bandpass filter to generate a signal that is constant frequency but follows different filter characteristics of the bandpass filter.

These matters are commonly used and known to those skilled in the art.

If the second frequency-determining element is an inductance, the sensor configuration according to the invention can be designed particularly easily.

In this case, a desirable configuration example of the control circuit for changing the inductance is a high-frequency core coil forming part of the inductance total magnetic circuit, at least a second coil is provided in this magnetic circuit, and the first coil is proportional to the arc length. It is preferable that the inductance of the frequency determining coil is changed by supplying the output signal of the measuring means to the second coil and causing a DC signal to flow through the second coil to bias magnetize the magnetic circuit. With this configuration, the operating point of the magnetic circuit can be preset to a desired value by appropriately presetting the bias magnetization coil, and therefore the inductance variation characteristics and the control characteristics of the entire circuit can be adjusted.

A capacitance diode may be used as the second frequency determining element, the capacitance of which is varied by a DC signal proportional to the arc length. Since both coils of the magnetic circuit are separated by a space and are not connected galvanically, the required high dielectric strength between the electric arc current source and the high frequency circuit can be easily achieved using the passive element with the above configuration. This sensor configuration can be used very effectively. That is,
During ignition of the arc, the spacing is adjusted completely automatically and without switching operations by means of a measuring signal proportional to the arc length. On the other hand, when the arc is extinguished, the switch is automatically switched and the interval is adjusted by an inductive or capacitive sensor.

This automatic switching is ensured by the second frequency changing element and its control circuit. In other words, when the arc is interrupted, L
The frequency of the C circuit is significantly different from the operating frequency set by the first frequency determining element. Each frequency operating range set by these two frequency changing elements is selected and separated by a frequency selection element, particularly a bandpass filter. As long as the frequency operating range of one frequency-determining element differs by at least 1.5 times from the frequency operating range of the other frequency-determining element, the signals can be very well separated.

Therefore, as soon as the second frequency determining element moves from its frequency stop range to the operating frequency range after the occurrence of the arc by the signal according to the arc length, the first frequency determining element t-L
By using a switching means that is separated from the C circuit and/or excavation circuit input, it is possible to reliably prevent the output signals of the two frequency determining elements from overlapping each other.

Embodiment The automatic welding machine shown in FIG. 1 includes an electrode holder 2 as a tool 1, and an electrode 3 supported by the electrode holder 2 is connected to a first output of a welding current source 5 via a cable 4. The second output cuff b of the welding current source 5 is grounded and connected to the steel plate workpiece 6 to be cut. The electrode holder 2 is movable in the height direction by a motor 9, thereby adjusting the distance between the electrode 3 and the workpiece 6 and the length of the arc 8. The motor 9 is driven by a regulation amplifier 10 which receives and takes regulation signals from a discriminator 11.

According to the length of the arc 8, the output cuff a, 7 of the welding current source 5
The b pressure varies within an operating range between approximately 150 and 160 volts, as shown in FIG. This output voltage is supplied to a bias magnetizing coil 12 which forms part of a magnetic circuit having two ferrite cores 12+z and 136. An insulating plate 14 is interposed between the ferrite cores 13α and 136, so that the high voltage welding current source 5 is reliably separated from the adjustment circuit described later. In ordinary adjustment devices, such isolation protection is obtained only by expensive isolation amplifiers, etc., but in the present invention, the magnetic circuit 1
This is done using simple and reliable elements such as 3a and 13M. Coil 15 wound around ferrite core 13cL
is connected in parallel with the coil 16. Coil 16 is also connected to capacitive sensor 17, and coils 15 and 1 are connected to each other.
6 and sensor 17 form an LC circuit.

The capacitance of the capacitive sensor 17 depends on the spacing between the sensor and the workpiece 6. LC circuits 15 to 17 are oscillators 18
is connected to the input of the oscillator to determine its oscillation frequency. Oscillator 1
Reference numeral 8 includes a setting resistor 19 used for frequency presetting. The setting resistor 19cL is used to preset the frequency and therefore the spacing between the tool and the electrode for arc machining.

The specific operation of the sensor configuration shown in FIG. 1 is carried out as follows. First, at startup, that is, before igniting the arc 8, the electrode holder 2 is moved above the workpiece 6 by the motor 9. A change in the spacing between the tool 1 and the workpiece 6 changes the capacitance of the sensor 17 and changes the oscillation frequency of the oscillator 18. The high frequency signal from the oscillator 18 is converted into a DC signal by the discriminator 11. sensor 17
is located a desired reference distance away from the workpiece 6, the output frequency of the oscillator 18 will be equal to the reference frequency and no voltage will be output from the discriminator 11. As a result, the motor 9 stops (see FIG. 4). On the other hand, when the distance between the tool 1 or the sensor 17 and the workpiece 6 is too large, the capacitance decreases and the oscillation frequency increases. Therefore, the output of the discriminator 11 becomes negative, this negative signal is amplified by the regulating amplifier 10, the motor 9 is activated and the tool 1 moves again towards the workpiece 6 □ This causes the capacitance of the sensor 17 to To increase, oscillator 1
8 gradually approaches the reference frequency, and when it reaches the reference frequency, the outputs of the discriminator 11 and the adjustment amplifier 10 become zero. This reference frequency and the corresponding tool/workpiece spacing are determined by the discriminator 11
It can be set by the setting resistor 11α. Furthermore, the oscillation frequency and hence the tool/workpiece spacing can be manually adjusted by varying the set resistor 19 of the oscillator 18.

When the arc 8 is ignited in operation, a voltage is generated in the bias magnetization coil 12. Magnetic circuits 13G and 13b are HF
Coil 1 because it is spread out in the core separation line area of the core.
5's inductance decreases. The holder 21 of the capacitive sensor 17 is raised by an electromagnetically actuated lift mechanism, and the sensor 17 is optically separated from the workpiece 6, so that the capacitance does not change even if the tool 1/workpiece 6 spacing changes further. . Thereafter, the frequency of the LC circuit will vary only due to variations in the inductance of the coil 15. Due to variations in the length of the arc 8, the welding current and therefore the voltage between the output cuffs a and 7b of the bath welding current source 5 vary.

Therefore, the current flowing through the coil 12 changes and the coil 1
5 changes, and the frequency of the oscillator 18 changes in the same manner as in the case of the change in the capacitance of the capacitive filter 15 described above. This causes the discriminator 11 to output an interval proportional signal. Output cuff a of welding current source 5
, 7b to coil 12.15, LC configuration 16
．． 17 and an oscillator 18, the interval proportional signal is not affected by interference voltages and induction phenomena that often occur in the environment of welding machines, etc., and passes through the line 18G to the discriminator 11. It is very effective. That is, the discriminator 11 outputs an output signal only in response to frequency variations and is not affected by voltage variations in the cable 186.

Furthermore, with this conversion configuration, capacitive sensor 1
It is now possible to carry out the adjustment via 7 and the adjustment for the arc length or arc voltage using a common evaluation circuit (oscillator 18, discriminator 11 and adjustment amplifier).

In the embodiment shown in FIG. 2, opposite elements are designated by the same numerals. In this configuration, the oscillator 18 includes a capacitor 18α, an amplifier 18d, an output resistor 186, as shown in detail.
It has a voltage output of 18ci.

Unlike the embodiment of FIG. 1, a capacitive diode 15 is connected in parallel with the variable capacitance of the capacitive sensor 170. As can be seen from this figure, this diode 15 is connected to the LC
This is the frequency determining element in circuit 16.15.17.

The capacitance of the diode 15 is varied by the voltage applied via the line 21 and a voltage amplifier 22 with a setting resistor 14 for gain adjustment. Amplifier 22 is connected to a series resistor 23 that conducts the welding current. resistance 23
Since the voltage drop at is simply increased by the amplifier 22, the capacitance of the diode 15 will be controlled by the welding current. Diode 15 due to voltage increase
The capacitance of the oscillator 18 decreases accordingly.
Since the frequency also changes, an output signal is generated from the discriminator 11 in the same way as described above, and a control signal for tracking is sent to the motor 9.

The embodiment shown in FIG. 3 is substantially similar to that in FIG. 2, but the capacitance diode 15 is replaced by piezoelectric elements 15a'i provided on both sides of the capacitor plate 15bk. This piezoelectric element 15α is connected via a line 21 to a voltage dividing circuit 14.22. Since the piezoelectric element 15α is physically distorted when the DC voltage of the line 21 fluctuates,
The distance from the electrode 156 changes, and its capacitance changes. Therefore, the LC circuit 1
5b, 17.16 frequencies change and the oscillator deviates from the reference frequency.

The sensor configuration of the embodiment shown in FIG.
has. The inductance of the induction sensor 23 changes as it approaches the workpiece 6, and therefore the LC circuit 23.17α
, 16 change, and the output frequency of the oscillator 18 changes. A second LC circuit consisting of coil 166 and capacitance diode 15 is also connected to oscillator 18.

Both LC circuits of this parallel configuration are in tune when a zero DC voltage signal corresponding to no arc is applied via line 21, and oscillator 18 oscillates in the frequency range Fl. The signal generated when the arc is extinguished is suppressed by the threshold circuit 24. The oscillator 18 operating in the frequency range F1 is the inductive sensor 2
When the signal deviates from this range due to the action of 3, the amount of change is detected by the discriminator 11α tuned to the frequency F1. The output signal of the discriminator 11α is supplied to the adjustment amplifier 10 (see FIG. 1) via the summing amplifier 25.The interval while the arc 8 is extinguished is adjusted by using the sensor 23 as in the above case. When the arc 8 is ignited, a higher DC voltage appears at the input of the threshold circuit 24, so that the threshold circuit passes this signal and the capacitance diode 15 enters its operating range. When the capacitance of the diode 15 changes drastically, the oscillator 18 changes from the previous frequency range F.
It deviates from 1. A frequency selective amplifier 26 coupled to the output of the oscillator 18 is tuned to this changed frequency, and its output signal opens the gate 27, causing the coil 16,
Capacitance 17α, inductive sensor 23 and oscillator 18
separate from the input. For this purpose, the oscillator 18 operates in the frequency range F2, the frequency varying element of which is provided by a capacitance diode having a capacitance that depends on the arc voltage and hence the length of the arc 8 (not shown). The signal in the frequency range F2 is converted into a DC signal by the discriminator 116 and supplied to the second input of the summing amplifier 25. Therefore, as long as an arc is present and the input voltage of the threshold circuit 24 exceeds its cutoff range, adjustment of the tool/workpiece spacing is effected only by measuring the arc voltage or current. However, the threshold circuit 2
When the voltage across F2 decreases and the capacitance of the capacitance diode 15 changes considerably, the oscillator 18 goes out of the frequency range of F2 and the frequency selective amplifier 26 no longer provides an output signal to the gate circuit 27. Closed again, the state of the sensor arrangement returns to operation in the frequency range F1, in which the frequency change and tool/workpiece spacing adjustment is performed solely by the inductive sensor 23. Therefore, a fail-safe effect can be obtained very easily.

It should be noted that in order to carry out all of the above-mentioned operations, the current and /-! shown in FIG. Alternatively, a variable inductance controlled by voltage may be used.

Frequency / provided in parallel with discriminators 11α and 11b
Digital converter 28 converts the output signal of oscillator 18 into a corresponding digital signal and supplies it to digital display device 29 . This display therefore shows the corresponding frequency value or the corresponding tool/workpiece spacing. Note that not only the display device but also the motor adjustment device may be operated by the digital output of the frequency/digital converter 28 instead of the analog output that valves the discriminators 11α and 11b.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a sensor configuration having the features of the present invention, and Fig. 2 shows a capacitance as the second frequency determining element.
To the diode! Figure 3 is a diagram showing a modification using a piezoelectric element as the frequency determining element; Figure 4 is a diagram showing the operating curve of the discriminator used in the sensor configuration; Figure 5 is a diagram showing the operating curve of the discriminator used in the sensor configuration. FIG. 6 is a diagram showing an example of a configuration in which a sensor is automatically separated when a measurement signal is generated. FIG. 6 is a diagram showing voltage characteristics of an arc or an arc current source. 2: Tool 6: Processed product 8: Arc (12, 13
G, 136, 14.15): Magnetic circuit (15, 16, 1
7): LC circuit 17: Capacitive sensor (for spacing) 15 (Fig. 1): Coil sensor (for arc) 15 (
Figure 2): Capacitance diode (for arc) 18: Oscillator 11: Discriminator 10: Adjustment amplifier 9: Motor 15α: Piezoelectric element (for arc) 15b: Capacitor electrode 11α: Discriminator (reference frequency 11) 11b: Discriminator (reference frequency/2) 26 Dual frequency selection amplifier 27: Gate circuit, −
9 α〕 rN m-fu -- C0 C 1to's ω Fu■ ■匡

Claims (15)

[Claims] (1) Measure arc voltage and/or arc current,
A method for determining the spacing between a tool and a workpiece of an electric arc processing machine, comprising: first measuring means for generating an electrical analog signal corresponding to the arc length from the measured value; Convert the analog signal to a high frequency signal, send this high frequency signal via a transmission circuit, in particular an electric line, to a regulator, pass it through a second converter and convert it back into an analog and/or digital signal, and send this signal to a display. and/or providing adjustment means for adjusting the spacing between the tool and the workpiece and adjusting the arc length. (2) In the method according to claim 1, the sensor has a second measuring means for measuring the interval via a capacitive or inductive sensor when the arc is extinguished or in an incomplete operating state. A method, characterized in that the sensor in the configuration is supplied with a high-frequency signal, which sensor is also connected to the converter, which converts the high-frequency signal into an analog and/or digital signal. (3) In a sensor configuration implementing the method according to claim 1 or 2, a conversion circuit means for converting a change in frequency into a change in voltage is provided, and the conversion circuit means converts a direct current signal or A sensor configuration comprising at least one variable frequency determining element whose frequency characteristics are variable according to a DC voltage signal, and supplying the variable frequency determining element with a DC signal proportional to arc current or arc voltage. (4) In the sensor configuration according to claim 3, the second measuring means for measuring the distance between the tool and the workpiece when the arc is extinguished or in an incomplete operating state,
The C circuit has a capacitive or inductive interval sensor as a frequency change element, the second measuring means has a second frequency change element whose frequency characteristics are changed by a control circuit, and the second frequency change Sensor arrangement, characterized in that the interval proportional signal of the first measuring means is fed to the control circuit in order to vary the frequency characteristics of the element. (5) The sensor configuration according to claim 4, wherein the second frequency changing element is an inductance, and the control circuit is configured to change the inductance. (6) In the sensor configuration according to claim 5, the inductance is a coil forming part of a magnetic circuit having a high magnetic permeability core that changes depending on the magnetic field, and the magnetic circuit includes: At least one second coil is provided, connected to the output signal of the first measuring means, which is proportional to the arc length, and the direct current flowing through this second coil causes a change in the magnetic field or the permeability of the core and thus the frequency. A sensor configuration characterized by varying coil inductance. (7) In the sensor configuration according to claim 4, the second frequency changing element is a capacitor whose capacitance changes according to a DC signal, and the output of the first measuring means whose capacitance is proportional to the arc length. A sensor arrangement characterized in that the capacitor is connected to the first measuring means so as to be changed by a signal. (8) The sensor arrangement according to claim 7, wherein the variable capacitance is a capacitance diode. (9) In the sensor configuration according to claim 7, the variable capacitor is a piezoelectric element having capacitor surfaces on both sides thereof, and this piezoelectric element is connected to the voltage output of the first measuring means. A sensor arrangement, characterized in that the spacing to the capacitor surface and thus its capacitance varies depending on the voltage signal of the first measuring means according to the arc length. (10) In the sensor configuration according to any one of claims 1 to 9, the LC circuit includes an oscillator whose oscillation frequency is changed by the first and/or second frequency changing element. A sensor configuration characterized in that it forms a part. (11) The sensor configuration according to claim 10, wherein the oscillator is a Clapp oscillator. (12) In the sensor configuration according to any one of claims 1 to 11, the second frequency change element and the control circuit that operates the second frequency change element provide arc control. the frequency of the LC circuit substantially deviates from the frequency determined by the first frequency changing element when the power is disconnected;
A sensor configuration characterized in that the frequency operating range defined by the two frequency change elements is separately defined by a frequency selection means, particularly a bandpass filter. (13) In the sensor arrangement according to any one of claims 1 to 12, the frequency operating range of one frequency varying element differs by at least 1.5 times from the frequency operating range of the other frequency varying element. A sensor configuration characterized by: (14) In the sensor configuration according to claim 12 or 13, the second frequency changing element enters its frequency operating range by a signal according to the arc length after arc ignition, and at the same time the first A sensor arrangement characterized in that it is provided with switching means for separating the frequency varying element from the input of the LC circuit and/or the oscillator. (15) In the sensor configuration according to any one of claims 1 to 14, the tool of the electric arc processing machine is provided with a first distance measuring/adjusting means, and the means includes:
a sensor operating in a non-contact mode and a second measuring means for measuring the arc current or arc voltage to produce a signal proportional to the spacing; both the sensor operating in the non-contact mode and the second measuring means; A sensor configuration characterized in that it is connected to a signal input of the first interval measuring/adjusting means.